Profichip VPC3+C - Isochron Mode (IsoM)

7 PROFIBUS DP Extensions
7.3.2 IsoM (Isochron Mode)
The IsoM synchronizes DP-Master, DP-Slave and DP-Cycle. The isochron
cycle time starts with the transmission of the SYNCH telegram by the IsoM
master. If the VPC3+C supports the IsoM, a synchronization signal at Pin
13 (XDATAEXCH/SYNC) is generated by each reception of a SYNCH
telegram. The SYNCH telegram is a special coded Global_Control request.
Cyclic
Service
Cyclic
Service
Acyclic
Service
Acyclic
Service
Token
Spare
Time
. . .
. . .
SYNCH
mesage
SYNCH
mesage
Cycle Time (T
DP
)
Cyclic
Part Part
Acyclic
gu lass 1)
Tw
VP
1.
2. auses a
DX_Out interrupt immediately, rather the event is stored in a flag. By a
following SYNCH message reception, the DX_Out interrupt and a
synchronization signa ated at the same time. Additionally a
w_G _Com and nte pt produced, as the SYNCH telegram
behaves like a regular Global_Control telegr
achin If D a_E chan e telegram p ce H
telegram, only the New_GC_Command interrupt is generated.
Fi re 7-15: Telegram sequences in IsoM with one DP-Master (C
o operation modes for cyclic synchronization are available in the
C3+C:
Isochron Mode: Each SYNCH telegram causes an impulse on the
SYNC output and a New_GC_Command interrupt.
Simple Sync Mode: A Data_Exchange telegram no longer c
l are gener
Ne C m i rru is
am to the DP state
m e. no at x g re des the SYNC
Bit Position
Byte
7 6 5 4 3 2 1 0
Designation
0 0 0 0 Control_Command
1
= 1
Group_Select
Group_8
Figure 7-16: IsoM SYNCH telegram
Each Global_Control is compared with the values that can be adjusted in
Control_Command_Reg (0Eh) and Group_Select_Reg (0Fh). If the values
are equal a SYNCH telegram will be detected.
64 Revision 1.03
VPC3+C
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